1. Field of the Invention
The present invention relates to a medical prosthesis for human implantation, and in particular, to an artificial ligament which is utilized to rebuild the ligament of a patient with a torn ligament.
2. Description of the Prior Art
A torn ligament is one of the most common sport injuries, and the anterior cruciate ligaments located at the knee joints have a very high incidence of tears during sport activities. The consequences of these tears are usually very severe which can lead to further structural damage such as ligament erosion, impaired joint function, and even disability, if treatment is not performed promptly and properly. Previously, surgeons attempted treatment by sewing the torn parts, but because ligaments have poor adherence and healing power, almost all of these attempts failed, so that such practices were abandoned.
Therefore, surgeons placed their hopes on rebuilding ligaments by transplantation. However, the biggest drawback of such a method is that it increases autoinjuries and leaves complications, sometimes to the extent that the drawbacks outweigh the benefits.
For example, using the patellar tendon as a replacement (in general, the connecting bones are also removed in the form of bone-patellar tendon-bone) for transplantation easily causes complications such as knee pain, patellar tendon contraction, and tendonitis, and complete success cannot be insured if the procedure is not done perfectly.
Another method uses tendons or ligaments as replacements by allogenic transplantation (i.e, from a fresh cadaver), but this method has two important drawbacks: (1) the source is scarce, and (2) the support measures are out-of-date, and very often the specimens are simply stored in low temperature refrigerators and utilized in transplantations after simple sterilization by immersing in a sterilizing solution, which cannot effectively eliminate antigens and kill all the bacteria and viruses which might be present in the cadaver body, nor can it prevent rejection or eliminate the risk of infections after transplantation.
Yet another method uses artificial ligaments as replacements for transplantation, and synthetic polymeric substances such as long strings or knitted bands of polyester, nylons, polytetrafluoroethylene, etc., are generally utilized as the replacements for transplantation, which normally produce good short-term effects. However, these synthetic polymers are different from body tissues with respect to their composition and structure, so that the risk of having aseptic inflammation due to chronic rejection is ever present. More importantly, polymeric materials have inherent creep deformation in nature and after a certain time of playing the function of ligaments, they are irreversibly elongated and lose the elastic function of ligaments. In recent years, attempts were made to prepare artificial tendons and ligaments from bovine tendons, and the specimens were utilized after simple freezing at low temperature (−80° C.), defatting and fixation by glutaraldehyde. Glutaraldehyde fixes proteins by crosslinking them and forming aldehyde acetals, but aldehyde acetal is not very stable and the resistance of the fixed substance to degradation is poor, which results in loss of the inherent mechanical strength due to degradation. In addition, the degradation slowly releases glutaraldehyde and generates toxic aldehyde radicals, and this is compounded by the problem that there is no antigenic treatment in the process to effectively eliminate the antigenicity, so that failures are often experienced due to chronic rejection when the specimens are transplanted into the body.
In light of the above reasons, there still remains a need for an artificial ligament which is utilized to rebuild the ligament of a patient with a torn ligament.